Pharmaceutical composition comprising L-carnitine for the treatment of impaired cardiac function

ABSTRACT

Further to the discovery that D-carnitine exerts an antagonistic effect versus the therapeutically advantageous effect of L-carnitine in the treatment of certain cardiac dysfunctions, a pharmaceutical composition is described for the treatment of such dysfunctions characterized by the fact that all the carnitine present therein is solely L-carnitine.

This is a continuation of co-pending application Ser. No. 558,563, filedon Dec. 5, 1983, which is a continuation of application Ser. No.187,654, filed on Sept. 16, 1980, both are abandoned.

The present invention concerns a pharmaceutical composition comprising Lcarnitine for the treatment of cardiac dysfunctions, and likewiseconcerns a therapeutical method comprising administering such acomposition to patients affected by such dysfunctions.

The therapeutical use of carnitine (β-hydroxy-γ-trimethylamino-butyricacid) in the treatment of cardiac arrhythmias and impaired cardiacfunction associated with congestive heart failure and cardiogenic shockhas already been disclosed in U.S. Pat. Nos. 3,830,931 and 3,968,241issued to De Felice.

It is likewise known the β-hydroxy-γ-trimethyl-amino butyric acidpresents an asymmetrical centre and hence occurs in the two stereoisomerforms D and L. In the aforementioned U.S. patents it is taught that ". .. either the racemate or the individual isomers can be employed. Whilethe racemate can be conveniently employed, it appears the L isomer ismore active while the D isomer is slightly more toxic". The prior artteaches therefore that, in the treatment of the aforementioned cardiacdysfunctions, the L form and the D form are both active, although acertain preference may be given to the L form versus the D form.

If it is considered that, as is well known, the resolution of a racemateinto the respective optical antipodes generally involves complex andexpensive processes, as in fact occurs in the case of the separation ofL-carnitine from D-carnitine, and that in the aforementioned patents itis affirmed that the racemic form can be suitably employed, it isevident that the prior art as a whole in no way suggests, at least inregard to the aforementioned therapeutical purposes, the separation ofthe optical antipodes for the employment of L-carnitine alone, butrather to simply use carnitine in its racemic form.

It has now been surprisingly found, and is the presupposition of thepresent invention, that, conversely to what is taught by the known art,in the treatment of certain cardiac dysfunctions and particularly ofthose disclosed in the aforementioned patents to De Felice, D-carnitineis not only slightly more toxic than L-carnitine, but even exhibits atrue and proper antagonistic effect against the therapeutical propertiesof L-carnitine. It must be well understood that it has been discoveredthat the D form is not simply inactive as compared to the L form, thatis it does not act as a simple "diluent" of the active L form, butrather it antagonizes, at least partially inhibiting the therapeuticallyadvantageous effect of L-carnitine.

Therefore the object of the present invention is a pharmaceuticalcomposition for the treatment of myocardial anoxia, myocardialischaemia, arrhythmic syndromes and heart failure, comprising aneffective amount of carnitine and characterized by the fact that saidcarnitine is solely L-carnitine.

For the purpose of the present invention the term "solely L-carnitine"means not only that the component of the composition consisting ofcarnitine is substantially pure L-carnitine, that is except for eventualimpurities or traces of D-carnitine, but also that carnitine, can be"prevailingly" L-carnitine, that is clearly exceeding the quantity ofD-carnitine present, for instance by an L:D ratio of 95:5.

It has likewise been found that a pharamecutical compositionparticularly suitable for the aforementioned therapeutical uses, when inthe unit dosage form, comprises from approximately 50 mg toapproximately 500 mg of L-carnitine.

Therefore the scope of the present invention also includes atherapeutical method for the treatment of patients affected bymyocardial anoxia, myocardial ischaemia, arrhythmic syndromes and heartfailure, characterized by the fact of administering to said patients,via the oral or parenteral route, a pharmaceutical compositioncomprising an effective amount of carnitine present solely in the Lform.

Although the daily dose to be administered depends, according to soundprofessional judgment, upon bodyweight, age, general conditions and thespecific affection exhibited by the patient, it has been found that itis generally suitable to administer to said patients from approximately2 mg/kg to approximately 10 mg/kg of bodyweight per day of L-carnitine.

The antagonistic effect of D-carnitine against L-carnitine has beenexperimentally demonstrated by means of the following techniques.

(A) Behaviour of L- and D-carnitine on adrenaline-induced stress onisolated rabbit heat

Male rabbit hearts weighing 1.6-1.8 kg were isolated as per the methoddescribed by O. Fanelli, Life Sciences, 23,2563-2570 (1978).

The hearts were perfused as per the Langendorff method (O.-Langendorff,Pfugers Arch. Ges. Physiol. 61,291-333, (1985) using a Ringer solution(which was not recycled) maintained at 38° C. and at a pressure 54 cm ofwater bubbled with pure oxygen.

The isometric contractions were recorded by a transducer attached via apulley to a clip on the apex of the ventricles and regulated in such amanner as to exert a tension force of 4 grammes. By means of anothertransducer connected to a volume displacement recorder the coronary flowwas monitored giving normal values: 22±4 ml/min.

The ECG was monitored using surface electrodes. Only hearts whichinitially showed a rate of at least 140 beats per minute were used.After a period of acclimatization lasting 25-30 minutes under theaforementioned experimental conditions, the basal values of the heartsto be treated with blank Ringer solution (controls) and standard Ringersolution containing L-carnitine or D-carnitine at the same concentrationof 1.10⁵ g/l were recorded for 15 minutes taking care to discard heartsexhibiting some irregularities.

Cardiac stimulation was achieved by injecting 0.5 ml of Ringer solutioncontaining 0.5 mcg of adrenaline using a lateral canula inserted intothe aortic bulb. This stimulation was repeated four times at 5-minuteintervals.

The stress tolerated by the heart for each injection of adrenaline wascalculated by the formula: ##EQU1## where Δg is the increasing tensionforce (in grammes) and Δf is heart rate (number of beats) during theperiod of time (in seconds) wherein the increase in tension forceoccurs.

The values referring to the control hearts were compared to therespective values obtained with the hearts perfused with Ringer solutioncontaining L-carnitine or D-carnitine, using Student's and Cochran-Cox's"t" test.

Results

Cornary flow

The basal values given in Table 1 show that L-carnitine slightlyincreases coronary flow, whereas D-carnitine does not.

Conversely, when adrenaline is injected D-carnitine increases thecoronary-dilator effect of adrenaline, whereas L-carnitine reduces it.

Tension force peak

The data given in Table 2 show that adrenaline-induced tension forcepeak is decreased by L-carnitine, while D-carnitine practically does notmodify it.

Duration of increased tension force induced by adrenaline

The data given in Table 3 show that the duration of increased tensionforce induced by adrenaline is shortened by L-carnitine, whereasD-carnitine lengthens it.

Heart rate

The data given in Table 4 show that adrenaline-induced tachycardia isreduced by L-carnitine and increased by D-carnitine.

Stress effect

The data given in Table 5 show that the stress effect is decreased byL-carnitine, whereas D-carnitine increases it.

Examination of the stress index (FIG. 1) shows that L-carnitine has anantagonizing effect on adrenaline-induced stress, while D-carnitineenhances it.

From the above experimental results it appears evident that L-carnitinereduces the three effects of stimulation on the heart exerted byadrenaline (see Tables 2,3 and 4), whereas D-carnitine even heightensthe adrenaline effect on the duration of tension force and heart rate.Consequently (see Table 5 and FIG. 1) the stress index is low in thepresence of L-carnitine and much higher in the presence of D-carnitine.

The antagonistic effect of the two optical isomers of carnitine is alsomade evident by the fact that L-carnitine reduces the coronary-dilatoreffect induced by adrenaline, whereas D-carnitine increases it.

(B) Effect on adriamycin cardiotoxicity in vitro study

The action of L-carnitine and D-carnitine against adriamycin-inducedcardiotoxicity was investigated using isolated rat heart perfused as perthe Langendorff method, with Tyrode's solution at the rate of 0.1ml/min.

The perfusion medium containing adriamycin at the concentration of 0.2mg/ml was perfused on the heart until heart rate was reduced by 30%compared to the basal value. This reduced heart rate was accompanied byreduced contractile force and coronary flow rate.

Successively, Tyrode's solution containing L-carnitine or D-carnitine ata concentration of 5.08 mM or Tyrode's blank solution (control group)was perfused on the heart for 90-120 min.

The graphs appearing in FIGS. 2, 3 and 4 show that the repairing effectagainst cardiac damage caused by adriamycin administration isexclusively exerted by L-carnitine, whereas D-carnitine exhibits anopposite effect antagonizing that of L-carnitine. D-carnitine appearsincapable of even partially restoring cardiac function.

(C) Effect on experimental infarctions (control infarction and testinfarction) induced in the same heart by occlusion of two coronaryarteries in the dog.

The technique described by W. Shaper, M. Hofmann, K. D. Muller, K. Genthand M. Carl in Basic Res. Cardiol., 74, 224-229 (1979) was employed,with simultaneous occlusion of two coronary arteries in the same heart,for producing ischaemic areas with equal dimensions in identicalhaemodynamic conditions.

Successively, one of the ischaemic areas was perfused with a D-carnitinesolution and the other with L-carnitine. Both solutions had the sameconcentration of carnitine (approx. 0.5 millimoles).

It was determined that, while the extension of the ischaemic areaperfused with the D-carnitine solution remained unchanged, the extensionof the ischaemic area perfused with the L-carnitine solution was reducedby approximately 60% as compared to the pre-infusion value.

                                      TABLE 1                                     __________________________________________________________________________    Isolated rabbit heart. Four adrenaline injections (0.5 mcg) with 5-minute     intervals                                                                     between injections. Changes in coronary flow ml/min.(mean ± S.E.)          no. of           adrenaline 0.5 mcg % values                                  Groups                                                                              hearts                                                                            basal values                                                                         1.sup.st injection                                                                   2.sup.nd injection                                                                   3.sup.rd injection                                                                   4.sup.th injection                      __________________________________________________________________________    Controls                                                                            9   23.6 ± 1.50                                                                       -0.76 ± 6.65                                                                      -5.86 ± 5.45                                                                      +7.85 ± 8.24                                                                      +12.74 ± 5.06                                                              (a)                                     L-carnitine                                                                         9   27.0 ± 0.91                                                                       -14.6 ± 6.43                                                                      +5.97 ± 5.38                                                                      +3.73 ± 6.08                                                                      +0.21 ± 4.05                         1 · 10.sup.-5 g/l                                                    D-carnitine                                                                         11  23.4 ± 1.02                                                                       -3.09 ± 3.01                                                                      +6.63 ± 6.16                                                                      +10.6 ± 3.48                                                                      +9.83 ± 2.62                         1 · 10.sup.-5 g/l     (b)    (c)                                     __________________________________________________________________________     Statistically significant values versus controls (a) 0.05>p>0.02, (b)         0.02>p>0.01, (c) 0.01>p>0.001                                            

                  TABLE 2                                                         ______________________________________                                        As in Table 1.                                                                Tension force increase peak (grammes) (mean ± S.E.)                                  adrenaline 0.5 mcg                                                          no. of            2.sup.nd                                                                             3.sup.rd                                                                             4.sup.th                              Groups  hearts  1.sup.st injection                                                                      injection                                                                            injection                                                                            injection                             ______________________________________                                        Controls                                                                              9       2.82 ± 0.41                                                                          2.92 ±                                                                            3.17 ±                                                                            3.43 ±                                                       0.32   0.35   0.59                                  L-carnitine                                                                           9       1.73 ± 0.23                                                                          2.23 ±                                                                            2.68 ±                                                                            3.02 ±                             1 · 10.sup.- 5 g/l                                                                   (a)       0.08   0.23   0.33                                  D-carnitine                                                                           11      2.48 ± 0.30                                                                          3.12 ±                                                                            3.13 ±                                                                            3.22 ±                             1 · 10.sup.-5 g/l                                                                              0.27   0.30   0.29                                  ______________________________________                                         Statistically significant differences versus controls (a) 0.05>p>0.02.   

                  TABLE 3                                                         ______________________________________                                        As in Table 1. Tension force                                                  duration (seconds) induced by adrenaline (mean ± S.E.)                               adrenaline 0.5 mcg                                                          no. of            2.sup.nd                                                                             3.sup.rd                                                                             4.sup.th                              Groups  hearts  1.sup.st injection                                                                      injection                                                                            injection                                                                            injection                             ______________________________________                                        Controls                                                                              9       49.2 ± 5.15                                                                          61.4 ±                                                                            61.0 ±                                                                            71.0 ±                                                       9.81   6.63   10.1                                  L-carnitine                                                                           9       37.8 ± 3.66                                                                          50.4 ±                                                                            55.7 ±                                                                            58.6 ±                             1 · 10.sup.-5 g/l                                                                              4.48   5.93   5.31                                  D-carnitine                                                                           11      73.5 ± 8.70                                                                          80.0 ±                                                                            83.5 ±                                                                            86.2 ±                             1 · 10.sup.-5 g/l                                                                    (a)       11.2   9.05   11.4                                  ______________________________________                                         Statistically significant differences versus controls (a) 0.05>p>0.02.   

                                      TABLE 4                                     __________________________________________________________________________    As in Table 1. Increase in heart rate, beats/minute (mean ± S.E.)          no. of           adrenaline 0.5 mcg                                           Groups                                                                              hearts                                                                            basal values                                                                         1.sup.st injection                                                                   2.sup.nd injection                                                                   3.sup.rd injection                                                                   4.sup.th injection                      __________________________________________________________________________    Controls                                                                            9   184 ± 6.5                                                                          +22 ± 13.5                                                                       +29 ± 3.5                                                                         +29 ± 6.8                                                                         +26 ± 11.8                           L-carnitine                                                                         9   178 ± 4.6                                                                         +33 ± 6.7                                                                          +32 ± 10.0                                                                        +44 ± 10.0                                                                       +33 ± 13.4                           1 · 10.sup.-5 g/l                                                    D-carnitine                                                                         11  177 ± 4.4                                                                         +53 ± 4.1                                                                         +46 ± 6.1                                                                         +53 ± 9.8                                                                         +46 ± 4.7                            1 · 10.sup.-5 g/l                                                                     (*)                                                          __________________________________________________________________________     (*)Statistically significant differences versus controls 0.05>p>0.02.    

                  TABLE 5                                                         ______________________________________                                        As in table 1. Effect of stress [∫Δg.t] · Δ         r/100 (mean ± S.E.)                                                                  adrenaline 0,5 mcg                                                          no. of            2.sup.nd                                                                             3.sup.rd                                                                             4.sup.th                              Groups  hearts  1.sup.st injection                                                                      injection                                                                            injection                                                                            injection                             ______________________________________                                        Controls                                                                              9       105.8 ±                                                                              182 ±                                                                             203.5 ±                                                                           294.6 ±                                            16.5      40.8   41.5   89.1                                  L-carnitine                                                                           9       48.0 ± 9.4                                                                           94.4 ±                                                                            153.0 ±                                                                           183.3 ±                            1 · 10.sup.-5 g/l                                                                    (c)       14.6   31.2   43.5                                  D-carnitine                                                                           11      255.4 ±                                                                              432.4 ±                                                                           425.2 ±                                                                           492.0 ±                            1 · 10.sup.-5 g/l                                                                    44.2 (b)  95.6   85.4   123.3                                 ______________________________________                                    

Two composition examples for the manufacture of tablets are givenhereunder

    ______________________________________                                        Example 1                                                                     ______________________________________                                        L-carnitine        330.0 mg                                                   Magnesium stearate  50.0 mg                                                   Microcrystalline cellulose                                                                       240.0 mg                                                                      620.0 mg                                                   ______________________________________                                    

    ______________________________________                                        Example 2                                                                     ______________________________________                                        L-carnitine        330.0 mg                                                   Stearic acid        35.0 mg                                                   Microcrystalline cellulose                                                                       230.0 mg                                                                      595.0 mg                                                   ______________________________________                                    

What is claimed is:
 1. A therapeutical method for the treatment ofpatients affected by arrhythmic syndromes and congestive heart failure,characterized by the fact of administering to said patients, via theoral or parenteral route, a pharmaceutical composition comprising aneffective amount of L-carnitine substantially free of D-carnitine. 2.The therapeutical method according to claim 1 characterized by the factof administering to said patients approximately 2 mg to approximately 10mg/kg of bodyweight per day of said composition.
 3. The method of claim2 wherein said L-carnitine is administered in tablets comprising 330.0mg L-carnitine, 50 mg magnesium stearate, and 240.0 mg microcrystallinecellulose.
 4. The method of claim 2 wherein said L-carnitine isadministered in tablets comprising 330 mg L-carnitine, 350 mg stearicacid, and 230.0 mg microcrystaline cellulose.